Reversible heat exchanger or regenerator systems

Abstract

A heat exchanger or regenerator system useable in an air separation plant to minimize infiltration of air into the low pressure nitrogen stream comprising a heat exchanger (regenerator) having at least one flow path for the reversing heat exchange fluids, which flow path has at each end, an inlet branch and an outlet branch, wherein each branch has two series connected valves with a vent pipe between each pair of valves. Fluid flow through the vent pipe is controlled, e.g. by remotely actuable switch valves.

I claim: 
     
       1. A method of operating a reversible heat exchanger or regenerator system which method comprises the steps of passing a first gas through said heat exchanger or regenerator via an inlet branch at a first or warm end of said heat exchanger or regenerator and an outlet branch at a second or cold end thereof whilst venting leakage gas through a first vent pipe associated with an outlet branch at the warm end of said heat exchanger or regenerator and a second vent pipe associated with an inlet branch at the cold end thereof; and subsequently passing a second gas at a lower pressure than said first gas, through said heat exchanger via the inlet branch at the cold end of said heat exchanger and the outlet branch at said warm end of said heat exchanger whilst venting leakage gas through a third vent pipe associated with the inlet branch at said warm end of said heat exchanger or regenerator and a fourth vent pipe associated with the outlet branch at the cold end thereof. 
     
     
       2. A method according to claim 1, wherein said first gas is air. 
     
     
       3. A method according to claim 2 wherein said second gas is substantially pure nitrogen.